I'm glad you got the problems resolved.

What you probably encountered were the after effects of bio-degradation of the your CYA (Stabilizer) over the winter. It can take as little as a week or two of 'slimy' conditions for your CYA to began to degrade.

When that happens, the follow-on chlorine demand will sometimes be very, very high. As you discovered, using dichlor or trichlor to correct is often not ideal.

You'll probably want to take steps to avoid this next winter.

(Welcome to the forum!)