There is conflicting information about this. This forum post claims they never went over 50% but had a short time with about 40% which enabled them to do some selfish mining with a reorg what enabled them to find 50% of the blocks for some time. Currently however data seems to suggest they have around 30%. According to this site, ~26% of the hashrate is of unknown origin (which could be Qubic, among others) and the rest are bigger Monero pools.

Apparently there was a massive social media attack going on to try to convince miners to join Qubic's pool, but they failed at that afaik.