My partner built a raised concrete pond and painted it with a blue fish friendly pond sealent. Weve had fish it it fine, gold fish and small local river fish. Ive bought many water lilies and potted them up in clay soil like ive read but they always seem to die as if they rotted.The leaves die off and it goes mushy. What would i be doing wrong? Out of about 10 lilies this red one is the only one left and it just stays like this with small leaves. It is winter now though so i don't expect much until spring.