Water in Cylinder

[RSchramm]

I have a 1991 Yamaha 250 I recently removed the spark plugs on cylinder 2, 4 & 6 The plugs are covered with white water/oily substance. I took the cylinder head off there is water in all three cylinders the 6 bolts down the center of the head were not very tight I think they might have loosened up I replaced head gasket 3-4 years ago and did not use screw lock the plugs in cylinders 1, 3, and 5 are clean

Hoping this is a head gasket failure any other possible causes?

[boats.net]

Check for holes corroded through cylinder head into water jacket. Might need to check inner exhaust plate for corrosion as well.