I trust Dave on the temperature thing because he's got smarts and much more experience than I do. Please forgive the long post, but I'm bad at being concise. I certainly don't intend to be critical, but some of the information can help stave off some common but easily avoidable problems. I'm suspicious about what's going on inside that pot. So tell us--how exactly do you water? Do you give a measured amount, or do you soak the soil? Was the plant's root ball very stiff and dry before you replanted it? What kind of soil did you use? Have you ever checked right after you water to be sure that the old soil gets moist? It's very strange for potting soil to need water more than once a week at most. That makes me think the old soil was very peaty and fine grained, and had become so compacted that it was hydrophobic. The best solution to that is to break up and remove all of the hardened soil and replace it with fresh soil, but this isn't a good time of year to do that kind of work. But simply submerging the pot in a bowl or bucket of water until no more bubbles come up (which may take a while) will rehydrate the compacted soil and make it easier for it to accept water normally. For moisture management, your finger is fine so long as it reaches all the way to the bottom. My concern is that your new pot has a reservoir to catch drained water, which can then be wicked up by the soil and keep the bottom wet. The issue is that roots need air to get the oxygen that lets them do their job, so they suffocate, rot, and die if the soil they colonize is wet for any length of time, and obviously can't supply the plant with water. This adds up to overwatering, which has almost the same symptoms as underwatering. Then the plant has to spend energy regrowing the lost roots, which eventually weakens it. That's why we tell people to remove the reservoir so the pot can drain into a saucer and to remove the drained water right away so it doesn't get taken up again. Lenore

how are you applying the fert.. and are you doing it in sun ... looks like fert may have washed down the leaf.. and puddled at leaf ends.. and maybe got burned ... i dont see any doom.. and i surely see no reason to destroy it all ... petunia need to be cut back a couple times during the season... when they start getting leggy ... i see no reason to do it too soon.. just because of a few brown leaf tips ... i also wonder about a cold event.. since you admit you planted too early ... and a minor cold snap.. may have caused what you see .. and its just showing now .... it never hurts to tell us where you are .. big city name ... zone alone is not good enough ... water when the pot needs water ... which in cool spring should not be very often ... you might be overwatering ... insert finger.. and FIND OUT ... and water when it needs it ... come the heat of summer.. more water will probably be needed ... but not right now ... also.. i see some seed pods forming.. you need to deadhead the pet's frequently ... to keep bloom going... ken

Very common problem. One reason I stopped growing asters; that and the rabbits. I was again tempted by theNY aster series "showtime" at a farmstand so I googled it on the spot. The Chicago Botanic garden had trials and in the report it said that many asters are disfigured by brown foliage at the bottom. I see that in other late bloomers.often cimigifugas...so I have wondered whether the stress of the growing season and variables in weather and water causes or contributes to browning. I think you need to pay attention to watering evenly....don't stress them with dry and wet.

Yes! That suddenly occurred to me after I posted. We did have a few days of freezing temps overnight. Is it frost damage? Can it recover?