For starters, running those monitors at 160Hz is too high, and I'm surprised they never generated an "Out of range" error.
Take the monitor(s) to a technician. A TV repair shop would be quite OK. Whilst most CRT monitors have adjustment for focus (blur) it is an internal adjustment, and unless you are quite familiar with working inside such appliances it is NOT a job to try yourself. The focus needs to be adjusted with the monitor working, and for the inexperienced a slight slip-up can potentially be a 'get dead' scenario!
Catweazle
Grandad
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