Just use these two optimizers:
var_list2 = [variables from first 6 layers]
var_list3 = [the rest of variables]
train_op1 = GradientDescentOptimizer(0.00002).minimize(loss, var_list=var_list2)
train_op2 = GradientDescentOptimizer(0.0002).minimize(loss, var_list=var_list3)
train_op = tf.group(train_op1, train_op2)
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