I don't think the upgrade is big enough. Really needs to be at least 3ft wide for silvers IMO. Asian aro and Jardini can get away with the size you proposed.
I might suggest a group of firemouths (x5) let them pair off. They grow quite slowly, so 150L could accommodate 2 pairs for a wee while, or one large pair plus dithers long term. Convicts are easy and under-rated, I have a very nice female with great colour and finnage but not fussed about finding her a male even though she deposits eggs every few weeks on her own.
50% waterchange, keep monitoring nitrogen levels - expect a rise in nitrite as ammonia comes down. How often are you doing waterchanges? What is the volume of the tank and what is the stocking level? What filter?
I have done worm treatments on my cichlids and they do flash occasionally but they never get welts. More likely to be the ammonia burn. Need to bring down that nitrate level, I believe nitrates may be linked to HLE disease.
I have some excess stock I need to move on. Two cuban cichlids, one is approx 7cm, the other is approx 12cm. The smaller one has a slightly bent neck.
Pick up only, need to move them this week.
Torbay, Auckland.