Looks like your doing a good job mate...flashing could be parasites or ammonia burn...are you doing regular water changes? but i wouldnt worry if they are only doing it every now and then...and they are way too young to be mating 
Also when my reds were that size...ghost shrimp and hikari pellets would bring out the colour in them more than anything else...good luck!
Also when my reds were that size...ghost shrimp and hikari pellets would bring out the colour in them more than anything else...good luck!
