So, you added some new convicts a week ago, then you saw ich, but not on the convicts you added a week ago? It's only on your pre-existing convicts?
Or, the ich is on the convicts you just added a week ago?
Regardless, if it was on the fish you didn't had before, then it's likely on all the fish now. Otoh, if it's on just the ones you just added, then all of the ones just added would have it, but perhaps some of the pre existing fish still don't.
I'd still treat them all, since they have all been exposed by now.
Heat at 86degrees and salt at 1 tsp per gallon x3 (6hours apart). Vacuum gravel and do water changes 50% a week. Get a powerhead to increase oxygen. Replace the amount of salt removed with the 50% water chngen Leave like this for 3 weeks and should go away. Don’t atop even when spots disappear.
Or can do meds like ich away or seahcem paragaurd. Pick one or the other treatment and not both.
Hard to say. Meds or salt might play havoc with the fry or the eggs. But my preference is heat and salt as
kno4te advised. Move quickly though since ich would probably be lethal to fry faster than for adults.