Let's view this as a learning experience. You can save these plants pretty easily and you have a bunch of time invested. Why give up now?!

Flushing isn't going to clear out the bat guano. But you still have options so long as you didn't over do it with the guano. What size are those pot they are in? It looks like they are 1 gallon or perhaps 3 gallon pots. Best case - those are 1 gallon pots (it's hard to tell from the pics). Re-pot them into 3 gallon pots or 5 gallon pots if they are currently in 3 gallon pots. Use your FF soil for the re-pot. Then start a careful watering regime - no nutes, 1/8 strength, 1/4 strength, etc. They will respond. There is nothing wrong with bat guano if used sparingly/carefully/correctly.

Just dial it back a bit. Those are nice looking plants. They are well established and can easily recover. Be patient. You should also consider soliciting advice in the Plant Problems forum. Some really crackers in there who can offer more directed advice.

EDIT: Just read through more of the thread... I see they are in 1 gallon pots. Re-pot into 3 gallon pots and you should be in good shape!