hye tnice....if u took them out of tank, where did u put them..??
with no pic, i assume it might be ich....u can either quarantine it or soak some food with garlic...if your mollys act normally, and eat normally, u can just feed them with some fish food which is already soak with garlic...
yes...definitely your tank is infected but your LR
is doing fine...the ich bacteria will need fish to be their hosts....once u have took your mollys out of tank and quarantine, 6-8weeks of time that bacteria in DT will die starving...but quarantine fish would only make them stress....fish have their own imune system....try to feed them with garlic+food and let them fight for it....do some frequent water change would also help....JMO