purple leaves soften an indication of phosphate deficiency. Discolored older leaves is often caused by a deficiency in nitrogen, Potassium, magnesium phosphate, chlorine, molybdenum or nickel. Your plants are basically removing these nutrients from the older leaves and moving them to the new leaves to support new growth. The old leaves then yellow and eventually die and fall off the plant. twisted leave is often cause by insufficient Calcium or magnesium.
Check your water GH (General hardness). GH is a measure of calcium and magnesium. Your tap water might not have enough. Most fertilizer don't have calcium and or they don't have enough calcium and magnesium. If your water is very soft you can use a GH booster to add some. Increasing water GH by one degree should be enough to resolve any GH issue.
Your fertilizer doesn't have any nitrogen, phosphate, and Calcium. Most people have too much nitrogen or phosphate due to fish waste so many fertilizer like yours don't have it. Seachem does sell a phosphate fertilizer bottle that can be used to increase phosphate. They also sell one that just has nitrogen. I prefer to keep a detectable but low level (1 to 5 PPM) of nitrate in my tank to insure I have enough nitrogen without harming the fish.
Note Flourish comprehensive doesn't have nitrogen. and doesn't have calcium. And in my experience not enough phosphate. And the iron and other metal i in it doesn't last long in the water. Many fertilizers work best when they are dosed daily and low levels.
Noet your fertilizer also does't have chlorine. Chlorine by itself is toxic. So plants prefer a chloride salt such s sodium chloride or potassium chloride. Plants need only atiny about of chlorine and tap water typically has enough chloride salts. So you should have to worry about chlorine.
